For centuries, scientists pondered the nature of light. Some thought it
was made of particles, others thought it was a wave. In 1905, Albert Einstein shed some light on the matter. He helped put everybody's
ideas together-and today scientists agree that light acts both as a wave AND a particle.

So what do we know about light? It consists of particles. These particles come in concentrated bundles of energy called photons. When
photons of light hit a metal surface, electrons are sometimes emitted from the metal's atoms. Light also travels in waves. In fact,
the energy of the emitted electrons depends on the wavelength of light that hits the metal. The shorter the wavelength, the more energy
these emitted electrons have. This is called the photoelectric effect. In 1921, Einstein won the Nobel Prize for his explanation of the
photoelectric effect.